This invention relates to semiconductor device manufacturing. More particularly, the present invention is directed to a simplified method for removing free halogen, in particular fluorine, from a halogenated polymer layer used as an insulating layer in a semiconductor device.
The integrated circuit manufacturing industry continuously progresses toward more highly advanced and miniaturized integrated circuits. With this progress toward smaller and smaller dimensions, the capacitive loading of wiring levels has become a more and more significant problem. Traditionally, SiO2 has been used to provide insulation between conductive areas. In order to reduce the capacitance of conductive areas, efforts have been made to use materials other than SiO2 to form insulating layers, that is, materials having a lower dielectric constant than that of SiO2. Various groups of materials have been identified and/or developed for this purpose, including various types of halogenated polymers, such as fluorinated parylenes (paraxylylenes) and fluorinated polyimides. Fluorinated parylenes, and methods of making them, are well known in the art (see, e.g., U.S. Pat. Nos. 5,268,202 and 5,879,808, the entireties of which are hereby incorporated by reference). Likewise, fluorinated polyimides, and methods of making them, are well known to those skilled in the art.
In the manufacture of semiconductor devices, it is frequently necessary to form vias through such insulating layers, which is typically accomplished by any of a wide variety of etching techniques known in the art, e.g., reactive ion etching (RIE). In the case of damascene techniques, wherein trenches are formed in insulating layers and filled with conductive material, it is necessary to etch processing channels for the wiring. It has been observed that when such etching techniques are applied to fluorinated polymers, free fluorine tends to be produced. For example, a well known and preferred type of etching technique for forming vias and/or trenches in insulating layers is reactive ion etching, e.g., using an oxygen plasma. When an oxygen plasma is used to form vias and/or trenches in a fluorinated polymer such as fluorinated parylene, a majority of the free fluorine which is produced exits the polymer in the form of F2O, but some free fluorine remains in the fluorinated polymer. Such free fluorine cannot be removed using oxygen plasma because such a treatment would cause further etching, thereby enlarging the etched areas beyond what is desired. Moreover, such further treatment would generate additional free fluorine.
Free fluorine produced in insulating layers can cause a variety of problems in semiconductor devices, e.g., it can diffuse into and contaminate other layers in the semiconductor device. Accordingly, in order to use fluorine or other halogenated polymers as insulating layers, it would be desirable, and in some cases it would be necessary, to either remove the free halogen and/or block the free halogen from diffusing into other layers in which free halogen is undesirable or deleterious.
Wang, et al., xe2x80x9cEvaluation of TaNx and Al as Barriers to Fluorine Diffusion from Fluorinated Parylenesxe2x80x9d discloses barriers which are designed to prevent free fluorine from reaching sensitive areas within semiconductor devices.
U.S. Pat. No. 5,380,401 discloses a method of removing fluorine contaminants from an aluminum-containing semiconductor bond pad, comprising exposing the bond pad to argon in a reactive ion etcher, and applying energy to the argon.
There is a need for a method of easily and effectively removing free halogen from insulating materials which contain such free halogen, e.g., free fluorine, without significantly adding to processing time or processing cost, and without etching or degrading the insulating layer, so as to avoid the need for adding a free halogen blocking layer to the device.
According to the present invention, there are provided simple methods which, as discussed in more detail below, provide for effective removal of free halogen from insulating materials which contain free halogen, in particular, a halogen-containing polymer which has been subjected to one or more etching techniques. The methods according to the present invention achieve such free halogen removal and do not significantly add to processing time or processing cost, without etching or degrading the insulating layer, thereby avoiding the need for adding a halogen-blocking layer.
According to one aspect of the present invention, there are provided methods of removing free halogen from a halogenated polymer, by contacting the halogenated polymer with hydrogen ions to generate hydrogen halide. The halogenated polymer is preferably contacted with the hydrogen ions at a temperature and pressure at which the hydrogen halide is gaseous. Alternatively, the temperature can be increased and/or the pressure can be decreased following generation of hydrogen halide to render the hydrogen halide gaseous.
There are further provided methods of forming semiconductor devices comprising contacting a free halogen containing insulating material layer of the semiconductor device with hydrogen ions.
In addition, there are further provided methods of forming semiconductor devices comprising, applying an insulating layer containing halogen onto a substrate, etching a pattern in at least the insulating layer, thereby generating free halogen in the insulating layer, and contacting the insulating layer with hydrogen ions to convert free halogen to hydrogen halide. The insulating layer is preferably formed of a halogenated polymer.
There are also provided semiconductor devices formed as described above. Although the invention is applicable to any halogen containing insulating layer, the invention is preferably used to remove free fluorine from a fluorinated polymer, preferably selected from the group consisting of fluorinated parylenes and fluorinated polyimides.
These and other features and advantages of the invention will become more readily apparent from the following detailed description of preferred embodiments of the present invention which is provided in conjunction with the accompanying drawings. The invention is not limited to the exemplary embodiments described below and it should be recognized that the invention includes all modifications falling within the scope of the attached claims.